The present invention generally relates to processing a resist on a semiconductor substrate. In particular, the present invention relates to a light-degradable surface coupling agent positioned between a semiconductor substrate and a resist, and associated methods and systems.
Microlithography processes for making miniaturized electronic components, such as in the fabrication of computer chips and integrated circuits, involve using photoresists. Generally, a coating or film of a photoresist is applied to a substrate material, such as a silicon wafer used for making integrated circuits. The substrate may contain any number of layers or devices thereon. In some instances, photoresists do not strongly adhere the semiconductor substrate surfaces. When photoresists do not adhere adequately to the substrate surface, undercutting and poor resolution typically result. Surface priming agents are therefore applied to a substrate just before a photoresist is applied to the substrate. Surface priming agents serve to increase adhesion between the substrate surface and the photoresist, especially organic photoresists.
The photoresist coated substrate is baked to evaporate any solvent in the photoresist composition and to fix the photoresist coating onto the substrate. The baked coated surface of the substrate is next subjected to selective radiation; that is, an image-wise exposure to radiation. This radiation exposure causes a chemical transformation in the exposed areas of the photoresist coated surface. Types of radiation commonly used in microlithographic processes include visible light, ultraviolet (UV) light and electron beam radiant energy. After selective exposure, the photoresist coated substrate is treated with a developer solution to dissolve and remove either the radiation-exposed or the unexposed areas of the photoresist (depending upon whether a positive photoresist or a negative photoresist is utilized) resulting in a patterned or developed photoresist. Many developer solutions contain water and a base, such as water and a hydroxide compound.
Development is a critical step in photolithography. This is because poor development decreases resolution, precise pattern formation and/or the quality of subsequent processing steps. For example, incomplete development followed by an etching step results in an incompletely etched underlayer, which in the case of an incompletely etched metal layer, may lead to short circuits. Poor development is caused by a number of factors. One factor is that a photoresist residue or a surface priming agent residue is frequently left by developer solutions. It is difficult to completely remove the photoresist residue and/or surface priming agent residue without deleteriously effecting the remaining patterned photoresist on the developed substrate surface.
In other words, the beneficial effects of surface priming agents (increased adhesion between a photoresist and a substrate) are diametrically opposed to the beneficial effects of not employing surface priming agents (easy removal of exposed portions of the photoresist during development). As a result, compromises must be made when conducting lithography.
The present invention provides a light-degradable surface coupling agent to simultaneously increase adhesion between a resist and an underlying substrate and promote removal of light exposed regions of the resist from the substrate during development, and associated methods and systems. Heretofore, improvements in adhesion between a resist and an underlying substrate result in difficulties in completely removing selected portions of the resist from the substrate during development. Similarly, improvements in easily removing selected portions of the resist from the underlying substrate during development result in decreased adhesion between the resist and the substrate. Therefore, the present invention contributes to improving lithography processing, which in turn, results in improvements in semiconductor device fabrication.
One aspect of the present invention relates to a semiconductor structure, containing a semiconductor substrate; a resist over the semiconductor substrate; and a light-degradable surface coupling agent between the resist and the semiconductor substrate.
Another aspect of the present invention relates to a method of processing a semiconductor structure, involving the steps of depositing a light-degradable surface coupling agent on a semiconductor substrate; depositing a resist over the light-degradable surface coupling agent; irradiating portions of the resist, wherein the light-degradable surface coupling agent under the irradiated portions of the resist at least partially decomposes; and developing the resist.
Yet another aspect of the present invention relates to a semiconductor processing system, containing a processing chamber operable to form a light-degradable surface coupling agent layer on a substrate in the chamber, a supply of a light-degradable surface coupling agent; and a measurement system for in situ measuring a thickness of the light-degradable surface coupling agent layer being formed and for providing a measurement signal indicative of the measured thickness.